2. Introduction
IEEE 802.11n is a next generation wireless technology
that delivers spectacular improvements in the reliability,
speed, and range of 802.11 communications. Delivering
about 6 times the data rate and 2-5 times the throughput
of 802.11a/g with substantial improvements in network
coverage and connection quality, 802.11n is expected to
replace wired Ethernet as the dominant local area network
technology of the future. This white paper examines the
operation of current generation wireless LANs, explains
key 802.11n technology components along with their
benefits, and explores 802.11n’s potential for delivering a
totally wireless enterprise.
3. 802.11n’s Current State • Frame Aggregation — 802.11n enhances
the MAC layer and reduces the transmission
overhead by allowing multiple data frames
The IEEE 802.11n working group, called Task Group N
to be sent as part of a single transmission.
(TGn), is working on publishing the 802.11n standard.
Further reducing the interframe spacing between
In March 2007 TGn approved the 802.11n Draft 2.0
frames allows transmissions to be completed in
which has become the early standard for several
a shorter amount of time, making the wireless
802.11n products available in the market today.
medium available for other transmissions, and
Availability and adoption of 802.11n Draft 2.0
increasing overall throughput.
products has been aided, to a large extent, by
the Wi-Fi Alliance’s announcement of a Draft 2.0
802.11n Draft 2.0 systems combine all of the above
interoperability certification program. The Wi-Fi
techniques to deliver connection speeds of 300
Alliance is an industry organization that certifies
Mbps with improved communication range and
the interoperability of 802.11 devices from different
more consistent coverage. While many 802.11n
vendors. Meanwhile TGn is continuing to work on
benefits can only be availed in an “N-only”
refining the 802.11n standard based on comments
environment (comprising of 802.11n access points
received from various experts. Based on current
and 802.11n clients), Draft 2.0 does establish
time lines, 802.11n is expected to achieve final
mechanisms for backwards compatibility with
IEEE Standards Board approval by November 2009.
802.11a/b/g devices and offers several benefits
even for existing 802.11a/b/g devices.
802.11n Overview
802.11n operates in two frequency bands: 2.4 GHz
802.11n introduces several enhancements to the for 802.11b/g/n and 5 GHz for 802.11a/n. A Phased
802.11 PHY (radio) & MAC layers that significantly Co-existence Operation (PCO) mode allows 802.11n
improve the throughput and reliability of wireless to dynamically switch between 20 MHz and 40 MHz
communication. These enhancements include: channels while communicating with 802.11a/b/g
and 802.11n devices, allowing for backwards
• Improved OFDM — A new, more efficient compatibility in both frequency bands.
OFDM (Orthogonal Frequency Division
Multiplexing) modulation technique that
provides wider bandwidth and higher
Understanding Radio
data rates. Frequency (RF)
• 40 MHz Channels — 802.11n doubles data Multipath & MIMO
rates by doubling the transmission channel
width from 20 MHz (used in 802.11a/g) In indoor environments, RF signals typically encounter
to 40 MHz. several barriers (walls, doors, partitions, etc.) in their
communication path towards the receiver. These
• Multiple-Input / Multiple-Output (MIMO) —
barriers either reflect or absorb the original RF signal,
A radio system (transceiver) with multiple inputs
creating multiple reflected or “secondary” waveforms.
into the receiver and multiple outputs from
Multipath results when multiple copies of the original
the transmitter capable of sending or receiving
RF signal travel different paths to arrive at the receiver.
multiple spatial streams of data (current 802.11
radios can transmit and receive a single data
Multipath traditionally has been considered the
stream on a single antenna used in a Primary/
enemy of RF communication. Multiple reflected
Secondary diversity configuration).
signals arriving at the receiver with varying delays
1 WHITE PAPER: 802.11n Demystified — Key consideration for n-abling the Wireless Enterprise
4. make it difficult for the receiver to separate a good receive signal processing. A MIMO radio can then
signal from poor quality signals. Weaker signals apply several techniques to enhance signal quality
may not be deciphered accurately, resulting in data and deliver more throughput. It is this ability to add
corruption and retries; furthermore, coverage holes signal components from multiple antennas that
can occur if reflected signals are out-of-phase but differentiates MIMO access points from traditional
are received simultaneously. access points that use antennas in a diversity
configuration. An access point with antenna diversity
The higher the multipath in an environment, the selects signal components from the antenna that
more the likelihood of poor RF performance resulting provides the best signal performance and ignores
from weaker received signal strength (RSSI), the other antenna.
increased retries, and dead spots. Conventional
RF system design has addressed the problem of A MIMO system has multiple Radio Frequency
multipath through the use of antenna diversity using (RF) chains implemented in the radio allowing the
two antennas for each radio in an access point. processing of multiple RF signals from multiple
Antennas in a diversity configuration function almost antennas. Depending on the number of transmit/
like redundant antennas. A signal from only one receive antennas and the number of spatial streams,
antenna is used at any time. Diversity switching logic a MIMO system is often classified as a TxR:S
implemented on the access point decides when system. Under this nomenclature T refers to the
to switch between the primary and the secondary number of transmit antennas, R refers to the
(diversity) antenna for receiving the best signal. number of receive antennas and S refers to the
number of spatial streams (transmitted data
MIMO introduces a new paradigm in RF systems streams) the system can process. For example
design. MIMO-capable radios actually perform a 3x3:2 system can transmit and receive 2 data
better within a multipath-rich environment. A MIMO streams on its 3 antennas.
system has multiple radio chains each of which is
a transceiver with its own antenna. A radio chain A MIMO-enabled access point (a radio system
refers to the hardware necessary for transmit/ supporting multiple radio chains) may employ
one or more MIMO techniques:
Maximal Ratio Combining (MRC)
To understand MRC, consider a traditional access point that implements diversity antennas. Depending on the
multipath caused by the environment, multiple RF signals will arrive on both antennas. The access point
samples its antennas and selects the preferred signal, ignoring the other signal. Diversity, in a sense, wastes
RF energy, using the signal from any one antenna for a transmission. MRC is a receive-side MIMO technique
that takes RF signals from multiple receive antennas and combines them within the radio to effectively
boost the signal strength. This MIMO technique is fully compatible with 802.11a/b/g devices and significantly
improves receiver sensitivity and overall gain for the access point radio, especially in multipath environments.
RF RX Chain #1
RF RX Chain #2 Demodulator Decoder Data
RF RX Chain #3
TX RX RF Receiver Digital Signal Processing
Figure 1: Signal Combining at Receiver
RF TX Chain #1
Data Encoder Modulator RF TX Chain #2
RF TX Chain #3
Digital Signal Processing RF Transmitter TX RX
2 WHITE PAPER: 802.11n Demystified — Key consideration for n-abling the Wireless Enterprise
5. Transmit Beamforming (TxBF)
Transmit beamforming, often abbreviated as TxBF, uses multiple transceivers with antennas (radio chains) to
focus RF energy toward the target receiver. An antenna array focuses energy toward the intended receiver
in a way that less energy is wasted in other directions. As discussed previously, a single RF waveform arrives
RF RX Chain #1
at the receiver as multiple waveforms and typically out-of-phase. The difference in phase can result in either
an attenuated, amplified, or corrupted waveform at the receiver. TxBF adjusts the phase of the RF signal at the
RF RX Chain #2 Demodulator Decoder Data
transmitter such that the receiver signal is an amplified waveform. Standards-based TxBF is only supported
for 802.11n clients. It requires the client to participate in the beamforming process by sending special frequency
RF RX Chain #3
characteristics and channel response information to the access point. This information is used by the AP in
calculating the phase adjustment for its next transmission. However, anyDigital Signal Processing
TX RX RF Receiver changes in the multipath environment
(movement of device, changes in obstructions) will nullify the beamforming phase optimization.
RF TX Chain #1
Data Encoder Modulator RF TX Chain #2
RF RX Chain #1
RF TX Chain #3
RF RX Chain #2 Demodulator Decoder Data
Digital Signal Processing RF Transmitter TX RX
RF RX Chain #3
Figure 2: Transmit Beamforming
TX RX RF Receiver Digital Signal Processing
Spatial Multiplexing RF TX Chain #1 RF RX Chain #1
Data Encoder Modulator RF TX Chain #2 RF RX Chain #2 Demodulator Decoder Data
Spatial multiplexing is the fullest and most powerful application of MIMO and involves the transmission of
RF TX Chain #1
spatial streams using N (or more) antennas.#3RF TX Chain Spatial multiplexingChain #3
RF RX requires a compatible MIMO client capable
of receiving and de-multiplexing N spatial streams. Each spatial stream carries a unique data stream
Data Encoder Modulator RF Transmitter Chain #2
RF TX TX RX
allowing the system to dramatically improve data rates and RF Receiver
Digital Signal Processing Digital Signal Processing
range. Spatially multiplexing MIMO systems are
represented as TxR:S, where T represents the number of transmit antennas, R the number of receive antennas
RF TX Chain #3
and S the number of spatial data streams. As stated earlier, a 3x3:2 MIMO access point can transmit and receive
2 data streams on itsSignal Processing The majority of 802.11n clients available in the marketplace canRX
Digital 3 antennas. RF Transmitter TX transmit and
receive 2 spatial streams.
RF TX Chain #1 RF RX Chain #1
Data Encoder Modulator RF TX Chain #2 RF RX Chain #2 Demodulator Decoder Data
RF TX Chain #3 RF RX Chain #3
Digital Signal Processing RF Transmitter TX RX RF Receiver Digital Signal Processing
Figure 3: Multiple Transmit Chains and Multiple Receive Chains
3 WHITE PAPER: 802.11n Demystified — Key consideration for n-abling the Wireless Enterprise
6. 802.11n PHY do not simply double to 96 sub-carriers. Instead,
they actually more than double to 114 subcarriers,
including pilots (which do not carry data). This allows
Although MIMO is the core building block for 802.11n, 802.11n to deliver a 65 Mbps data rate (instead of
MIMO alone cannot deliver high throughput. The 54 Mbps) per 20 MHz channel for a total of 135
802.11n physical layer (radio) implements wider Mbps on a 40 MHz channel when transmitting a
channel width along with improved modulation single spatial data stream. When transmitting using
techniques that provide a high bandwidth medium for 2 spatial streams on a 40 MHz channel, this data rate
multiple spatial data streams. As an analogy, if MIMO’s again doubles to 135 Mbps x 2 — 270 Mbps.
spatial multiplexing delivers 2 trains, the 802.11n
PHY provides 2 separate tracks on which to run the The 802.11-2007 standard dictates that every bit
2 trains, thereby doubling the transport of packets transmitted over the air is represented as a symbol.
and increasing throughput. 802.11b transmits 1 symbol per microsecond for its
1 Mbps data, 2 symbols per microsecond for its 2 Mbps
Improved OFDM and Channel Bonding data rate and so on. An 802.11a/g symbol is transmitted
for 4 microseconds and packs many more bits — up
802.11b radios use DSSS modulation on a channel that to 216 bits for the 54 Mbps data rate.
is 22 MHz wide to deliver data rates between 1 Mbps
and 802.11 Mbps. 802.11a and 802.11g both use OFDM symbols are separated by a guard interval
20 MHz channels, with OFDM modulation to deliver (GI) to reduce inter symbol interference. Since no
data rates between 6 Mbps and 54 Mbps. The table bits or data is transmitted during this time, the
below shows the relationship between the spreading GI is typically an overhead to the communication
methods, modulation techniques and summarizes process. The longer the GI between symbols,
these data rates. the lesser the throughput. 802.11a and 802.11g
symbols are separated by an 800ns GI. 802.11n
One of the reasons 802.11a and 802.11g offer introduces the concept of a short GI (400ns). In a
higher data rates than 802.11b is they use OFDM high-multipath environment, a long GI setting will
modulation techniques. typically improve overall RF performance, whereas
in low multipath environments, a short guard setting
802.11n uses a more efficient OFDM modulation and can be more advantageous.
can use 40 MHz channels. This more than doubles
the data rate for 802.11n when compared to 20 MHz As noted earlier, when transmitting 2 spatial streams
channels. When operating within a traditional 20 MHz in a 40 MHz channel, 802.11n supports data rates
channel, OFDM further slices the channel into 52 of up to 270 Mbps. However, when operating with
subcarriers (48 of which are used for carrying data). a short GI 802.11n further improves data rates to
However, when 802.11n applies OFDM on a 40 MHz deliver a top speed of 300 Mbps.
channel, the number of data-carrying subcarriers
DSSS CCK OFDM
Modulation BPSK BPSK QPSK BPSK QPSK 16-QAM 64-QAM
Data Rate
1 2 5.5 11 6 9 12 18 24 36 48 54
(Mbps)
802.11b
* * * *
(2.4 GHz)
802.11g
* * * * * * * * * * * *
(2.4 GHz)
802.11a
* * * * * * * *
(5 GHz)
Table 1: Modulation Techniques and Data Rates
4 WHITE PAPER: 802.11n Demystified — Key consideration for n-abling the Wireless Enterprise
7. One Spatial Stream (MCS 0-7) Two Spatial Streams (MCS 8-15)
802.11n 802.11n 802.11n
802.11a/g Mandatory Mandatory Short Guard Two Spatial Mandatory Short Guard
Rates Rates (20 MHz Rates (40 MHz Interval Enabled Streams Rates (40 MHz Interval Enabled
channel) channel) channel)
6 6.5 13.5 15 13 27 30
9 13 27 30 26 54 60
12 19.5 40.5 45 39 81 90
18 26 54 60 52 108 120
24 39 81 90 78 162 180
36 52 108 120 104 216 240
48 58.5 121.5 135 117 243 270
54 65 135 150 130 270 300
Table 2: MCS Rate Index
802.11n Frame IP header and the IP packet payload from layers
4-7. When Mobile Units (MUs) communicate with
Aggregation Techniques different hosts in a network they still send all the
802.11 frames to the access point. Access point
802.11 communication uses a shared medium that receives the 802.11 frames and forwards them to
has a significant amount of overhead associated it. appropriate destinations. This may involve adding
Unlike wired Ethernet, there is no collision detection an 802.3 header if the destination is a wired host or
mechanism available in the wireless medium. Every a new 802.11 header if the destination is an 802.11
wireless frame requires a positive Acknowledgement wireless host. The MSDU aggregation technique
(ACK). This requirement for transmitting an ACK exploits this behavior and allows for a mechanism to
frame for every control/data frame has a huge aggregate multiple payloads in a single 802.11 frame.
performance penalty and significantly reduces Since the MU has a single security association with
throughput of 802.11 communication systems. the access point, this large 802.11 frame incurs
802.11 devices are also required to use a random the overhead of encryption (and decryption at the
wait interval (backoff period) after transmitting a receiver) only once! This improvement is more
frame and before getting access to the medium pronounced for small size frames.
to transmit the next one. This further reduces
Since an A-MSDU frame is transmitted as a single
aggregate system throughput.
802.11 frame, receiver can acknowledge by sending
802.11n introduces 3 key enhancements which a single ACK frame. There is also a significant
address the inefficiencies of the traditional 802.11 increase in the maximum frame payload which
MAC layer. Two of these techniques rely on frame reduces the acknowledgement overhead associated
aggregation; the third technique reduces interframe with 802.11 communications and improves overall
spacing between transmissions. throughput. The maximum A-MSDU size allowed by
802.11n is 8192 bytes. The disadvantage of aggregating
A-MSDU is that each frame is only protected by a
MSDU Aggregation single checksum and an error in receiving an A-MSDU
transmission incurs the overhead of having to
The term MSDU (MAC Service Data Unit) refers to
retransmit the entire A-MSDU again.
the payload that is carried by the 802.11 MAC layer
frame. An MSDU typically consists of an LLC header,
5 WHITE PAPER: 802.11n Demystified — Key consideration for n-abling the Wireless Enterprise
8. Figure 4: 802.11n Frame Aggregation with Block Ack
MPDU Aggregation with Block ACKs DIFS is the minimum idle time for transmissions
if the medium is idle for longer than the DIFS
MPDU (MAC Protocol Data Unit) aggregation gathers interval. Wi-Fi Multimedia (WMM) based QoS
802.11 frames, which each already have an 802.11 allows frame bursting for certain devices without
header for the same destination and transmits them requiring a random backoff. These WMM devices
as a single frame. Since this process involves typically separate their ACK receipt and subsequent
transmitting multiple 802.11 frames as a single transmissions with a shorter interframe spacing,
“grouped” frame, each frame requires it own ACK; referred to as Short Interframe Spacing (SIFS).
however, instead of transmitting each ACK 802.11n introduces an even shorter interframe
individually, 802.11n introduces a Block ACK frame spacing called Reduced Interframe Spacing (RIFS).
which compiles all the individual acknowledgements
into a single frame which gets transmitted from
the receiver to the sender. The Block ACK frame is
802.11n Beacons &
essentially a bitmap, or matrix of which frames are
being acknowledged.
Mixed Mode Operation
802.11n beacons are sent on a regular 20 MHz
One of the disadvantages of MPDU aggregation is
channel using a low rate modulation. Beacons in
that each 802.11 frame needs to be encrypted
the 2.4 GHz frequency are fully understood by
separately, adding encryption overhead. On the other
802.11b/g devices and 5 GHz beacons are fully
hand, MPDU aggregation allows for the selective
understood by 802.11a devices. An 802.11n beacon
retransmission of those frames not acknowledged
contains additional High Throughput (HT) operational
within the Block ACK. This can be very useful in
information about the access point including channel
environments which have a high number of collision
width (20/40 MHz), guard interval, and number of
or transmission errors. The maximum A-MPDU size
spatial streams (usually 2). An 802.11n beacon also
allowed by 802.11n is 64K bytes.
contains frame aggregation information, such as the
maximum MSDU and MPDU sizes. Due to all this
Reduced Interframe Spacing (RIFS) extra information carried in the 802.11n beacon, the
size of the 802.11n beacon frame is much larger
Normal 802.11 transmitters are required to implement than the conventional 802.11a/b/g beacon. 802.11n
a random backoff between transmissions. DCF is fully backwards compatible to support mixed
(Distributed Coordinated Function) is a contention- mode operation with 802.11a/b/g devices.
based service widely implemented in infrastructure
networks that defines the backoff period for devices. The backwards compatibility 802.11n provides
The interframe spacing in DCF is referred to DCF is similar to the protection mechanism 802.11g
Interframe Spacing (DIFS).
6 WHITE PAPER: 802.11n Demystified — Key consideration for n-abling the Wireless Enterprise
9. provides for 802.11b devices. 802.11n provides this newly-introduced radar pulses. The operation of
protection mechanism in both bands, 2.4 GHz (for these access points is limited to only those bands
802.11b/g devices) and 5 GHz (for 802.11a devices). that do not require radar detection, significantly
As with 802.11g, the protection mechanisms kick reducing the number of available channels and
in as soon as an access point hears a legacy device overall system throughput.
transmitting on the same channel. The legacy device
does not have to be associated to the 802.11n
access point; the access point just needs to hear Adopting 802.11n
it on the same channel. However, mixed mode
operation reduces the overall throughput for 802.11n 802.11n RF Network Planning
cells. Keeping legacy clients on a different channel
and dedicating separate channels for 802.11n RF network design typically involves determining
devices can help resolve this problem. the number of access points, their placement,
channel assignment, and power settings to deliver
Frequency Bands and the required coverage and throughput for a given
physical environment. Traditionally, RF network
Channel Availability design has evolved from a series of physical site
surveys, in some cases, to combining physical site
surveys with predictive planning tools.
As noted previously, 802.11n can operate in both
the 2.4 GHz and 5 GHz frequency bands and is
The RSSI-based RF planning tools of the past are
fully backwards compatible with current generation
of little use in predicting and characterizing system
devices in each band. 802.11g and 802.11a use
performance for an 802.11n network. Planning tools
channels that are 20 MHz wide, while 802.11n can use
must take into account the multipath characteristics
20 or 40 MHz channels when communicating with
of a wide variety of building construction material like
other 802.11n devices. The 2.4 GHz frequency band
concrete, glass, dry-wall, office cubicles, warehouse
has a total of 3 non-overlapping 20 MHz channels,
racks, etc. In addition accurately characterizing
while the 5 GHz band has a total of 23 non-overlapping
multipath is extremely important for optimal MIMO
20 MHz channels (for most countries). For 40 MHz
performance. Multipath characterization includes
802.11n communications, this means the 2.4 GHz
analyzing the geometrical structure of site drawings
band offers only a single 40 MHz non-overlapping
representing the actual physical dimensions of the
channel, while the 5 GHz band offers up to 802.11
intended radio coverage area.
non-overlapping 40 MHz channels. At a connection
speed of 300 Mbps, a 2.4 GHz deployment can
Because 802.11n uses MIMO transmissions with
deliver aggregate data rates up to 450 Mbps (a single
multiple data streams of varying modulation, this
40 MHz 802.11n channel at 300 Mbps and a single
analysis of the in-building multipath characteristics
20 MHz 802.11n channel at 150 Mbps or three
must be combined with knowledge of the predicted
20 MHz channels at 150 Mbps), whereas the 5 GHz
RSSI in order to arrive at an accurate prediction of
deployment can deliver 3.45 Gbps (11 high throughput
the system performance. Thus, merely predicting
40 MHz 802.11n channels at 300 Mbps each and a
RSSI at any given point is of little or no value.
single 20 MHz 802.11n channel at 150 Mbps).
802.11n requires a system capable of combining the
effects of MIMO with multiple spatial streams and
Clearly, the 5 GHz UNII band is better suited for
the underlying RSSI.
multi-cell RF deployments; however, there are
two issues that need to be considered with the
When supporting existing 802.11b/g clients and
5 GHz frequency band. The 5 GHz band’s range
simultaneously deploying 802.11n in the 5 GHz
is a little less than that of 2.4 GHz, and there are
band, there is no easy way to insert new 802.11n
radar detection requirements within this band. The
access points without causing harmful co-channel
range issue can be easily overcome with the proper
interference. Even with a rip and replace migration,
antenna selection and transmit power adjustment.
a one-to-one replacement of legacy access points
The second issue requires the 802.11n radio chip
with an 802.11n AP (without transmit power
set provide radar detection and dynamic frequency
adjustment) is likely to cause interference issues
selection (DFS) capabilities. Many early 802.11n
given the improved receiver sensitivity of the new
access points (even those that are Wi-Fi Draft-N
radio technology.
certified) use radio chipsets that cannot detect some
7 WHITE PAPER: 802.11n Demystified — Key consideration for n-abling the Wireless Enterprise
10. 802.11n planning can be simplified by using planning unmonitored and open for attack for longer periods
tools designed specifically for 802.11n and that of time. The time-slicing problem becomes more acute
offer legacy deployment support. Customers should with 802.11n, because each WLAN channel must
look for tools that drive RF heat-map algorithms now be monitored for attacks at both the 20 MHz
based on the detailed RF characterization of the and 40 MHz channel widths. This almost doubles
specific access point radio deployed. Predictions the number of channels the sensor has to monitor.
and coverage maps generated for generic access 802.11n access points optimized for high throughput
point models can provide misleading results, spend fewer cycles monitoring. Leaving several
delivering inconsistent coverage and poor channels unmonitored for long periods of time
performance when deployed. exposes the wireless network to serious threats.
802.11n Security Issues A dedicated sensor radio that does not serve
WLAN clients (or perform wireless bridging or
The high throughput and reliability benefits of meshing) is able to spend all its time scanning for
802.11n will likely drive a greater proportion of rogues and attacks, thus providing a much higher
new LAN deployments to be completely wireless. level of wireless security. A dedicated sensor can
However, the need for security becomes even intelligently adjust its frequency scanning pattern
greater as businesses move mission critical based on wireless activity, spending more time on
applications to wireless and make it a primary channels of interest, actively terminating rogues
network. A comprehensive WLAN security policy and unauthorized wireless sessions, without being
enforced by a dedicated Wireless Intrusion constrained to a single operational channel.
Prevention System (WIPS) system provides the
foundation for wired-to-wireless network transitions. Indoor 802.11n MESH
Part-time WIPS can utilize the wireless infrastructure Mesh technology enables access points to
for limited detection of wireless attacks and rogue wirelessly connect to each other and transmit data.
devices. These systems use access points that can Mesh provides a great way to extend network
service WLAN clients on one channel and perform coverage, typically within hard-to-wire outdoor
off-channel scanning to detect rogue devices deployments. A dual-radio access point design
and to capture threats for analysis. The access allows deploying one radio for WLAN client access
point forwards information to a WIPS server that while leaving the second radio for a mesh backhaul.
compares them against a database of well known In 802.11a/b/g access points, the 802.11a radio was
attack signatures to identify patterns and generate typically used for mesh backhaul and provided a 54
events and/or alarms. Although the throughput of Mbps connection to the network. With 802.11n, the
a typical 802.11n access point is expected to be data-rate of this backhaul link increases to 300 Mbps,
about 6 times that of a traditional 802.11a/b/g access making mesh a higher speed network than Fast
point, with improvements in hardware (faster CPUs, Ethernet for interconnecting access points.
increased memory), most access points can handle
both data and WIPS functions. It is important to note that bandwidth alone is not
all that is involved in replacing wired access points
Part-time WIPS is sub-optimal for monitoring 802.11n with wireless mesh connections. Typically, local
deployments. Time-slicing radio resources for performing area networks are segmented using Virtual LANs
off-channel scanning is likely to have a serious impact (VLANs), each with its own quality of service (QoS)
on latency-sensitive and bandwidth-intensive and security requirements. To replace a wired
applications like voice and video. Optimizing the connection with a wireless link, the mesh access
radio’s configuration to spend more time servicing point should support intelligent backhauls that are
WLAN clients, with fewer off channel scans, can VLAN and QOS-aware, supporting WPA2 security
improve WLAN performance but leave more channels on the wireless link.
8 WHITE PAPER: 802.11n Demystified — Key consideration for n-abling the Wireless Enterprise
11. The Wireless Enterprise
Mesh resiliency is another important consideration.
Any changes in the physical environment can
802.11n offers many benefits to an Enterprise customer. In addition to high-
significantly change RF performance. For example,
speed connectivity and better range for 802.11n clients, the new standard
the movement of goods within a warehouse could
also delivers significant improvements in WLAN reliability and coverage for
temporarily downgrade the RF link between two
existing 802.11a/b/g deployments. The following are some examples of
access points to unusable levels. Consequently, mesh
high-bandwidth applications that can take advantage of 802.11n:
APs must maintain multiple redundant backhaul
connections to other access points and dynamically
• Education — Wireless access in high density areas, like classrooms
self-heal based on changing RF conditions.
and auditoriums, with fewer access points
With the correct set of access point configurations,
• Healthcare — Bedside access to medical imaging and patient records
802.11n-based mesh provides a great opportunity
to reduce the number of wired access points in • Manufacturing — Wireless sensor networks and video surveillance
an indoor WLAN and replace them with a mesh
design that saves cabling costs and delivers a • Retail — Store-of-the-future applications, like smart carts with
higher performance network. location-based advertisement streaming, wireless digital signage,
and video surveillance
In high-multipath environments (e.g. manufacturing, warehouses, etc.),
802.11n will also deliver a more reliable wireless network with better
coverage and fewer RF dead spots. All things being equal, 802.11n is
expected to deliver a significantly better wireless experience compared to
the existing WLAN technologies and standards. With 802.11n, wireless
networking catches up with wired networking in the area of predictability
and reliability and exceeds Fast Ethernet in speed and throughput.
The high-bandwidth and improved reliability of 802.11n, when combined
with the roaming benefits of wireless connectivity, will fundamentally
transform the end-user mobility experience, impacting end-user behavior
and business processes within the enterprise. With 802.11n, wireless
will no longer be the network of convenience, and in many cases, will
be the primary edge network running the most critical applications. For
the enterprise CIO, 802.11n lowers the cost of ownership for deploying,
supporting, and managing a WLAN. In addition, business applications now
can be defined for a single mobile device platform without the need for
developing and porting to multiple platforms. Employees will have reliable
“anytime, anywhere” access to all business applications. Customers
are better served by employees with seamless access to business
information systems, regardless of location or device type. Traditional
wireless networking enabled enterprise mobility in select verticals, allowing
key applications to be wireless-enabled. 802.11n can unwire almost any
business application used in the enterprise today and support seamless,
location-independent information access for the workforce, reducing
infrastructure/platform costs while enhancing productivity levels and
improving customer satisfaction.
802.11n enables, “The Wireless Enterprise”; an IT-enabled business
strategy that leverages wireless systems and applications to drive dramatic
improvements in workforce productivity and customer satisfaction. From
package delivery to warehouse and store operations, wireless technology
has already improved business processes for verticals and retail. In the next
3-5 years, high-speed, reliable and user-friendly wireless technology will
revolutionize the way businesses communicate, collaborate, and service
customers. The future of the network is wireless. It’s time to cut the wire
and become a smarter, more efficient wireless enterprise.
